1. Field of the Invention
This invention relates to a retractor for winding the webbing of seat belts which is provided in a vehicle to restrain a seat belt wearer in case of emergency, and more particularly to improvements in emergency locking retractors adapted to restrain or lock the pulling-out or unwinding of the webbing by an acceleration or deceleration applied suddenly to the vehicle body.
2. Description of Related Art
In recent years, it has become compulsory for vehicle drivers and fellow-passengers to wear seat belts in many countries in order to prevent them from being killed, getting hurt or being physiologically injured in traffic accidents. In general, a seat belt comprises a webbing for restraining a seat belt wearer, a buckle for wearing this webbing, and a retractor for controlling the unwinding and rewinding of the webbing. A variety of devices are provided on the retractors for controlling the unwinding and rewinding of the webbing. As for such retractors for seat belts, there are Automatic Locking Retractors (ALR) wherein when the unwound webbing is once rewound operationally it cannot be pulled out any longer, and Emergency Locking Retractors (ELR) wherein an arrangement is made such that the acceleration applied to the vehicle body is detected, and when the detected acceleration exceeds a predetermined value, it becomes impossible to pull out the webbing. In case a seat belt is used to fix a child safety seat securely onto a seat in a vehicle, the Automatic Locking Retractors are arranged such that when the webbing is once rewound it becomes impossible to pull out and it is superior, in the restraint point of view, to the Emergency Locking Retractors adapted to restrain the pulling-out or unwinding of the webbing only in the case of an emergency. However, the Automatic Locking Retractors pose a problem in that, because they restrain seat belt wearers all the time, the wearers cannot move their bodies freely thus causing the wearers to feel uncomfortable.
In view of such situations, there has been developed in recent years a retractor for seat belts which can fulfill the function of both the ALR and the ELR and can be used selectively as either the ALR or ELR in such a manner that when the webbing is pulled out in full length from the retractor it may function as the ALR type seat belt, while in other conditions it may function as the ELR type seat belt. (For example, reference is to be made to U.S. Pat. No. 4,436,255.) U.S. Pat. No. 4,436,255 specification discloses a retractor for seat belts which comprises, in combination, a retractor which is comprised fundamentally of a ratchet wheel fixed to a webbing take-up shaft and a pawl engageable with the ratchet wheel so as to stop the unwinding rotation of the webbing from the take-up shaft; an inertia lock mechanism; and cam means which is comprised of a cam member and a follower member, the arrangement being made such that when the webbing is pulled out in full length to restrain the wearer the pawl is engageable with the ratchet wheel, and when the webbing is unwound by a predetermined amount from the take-up shaft, the take-up shaft is rotatable in either direction, but when the inertia lock mechanism is actuated in a vehicular emergency situation the rotation of the take-up shaft is stopped.
However, this automatic-emergency locking retractor for seat belts has been disadvantageous in that it is arranged to be changed over to ALR type seat belt by rewinding the webbing to some degree after it has been pulled out nearly in full length. In other words it cannot be changed over to ALR unless the webbing is pulled out once nearly in full length and then rewound by some amount. Further, the inventor of the present invention developed previously a retractor for seat belts which can fulfil both functions of ALR and ELR and can be used selectively as either ALR or ELR in such a manner that when the webbing is pulled out nearly in full length from the retractor and when the webbing has once been locked it may function as ALR, while in other conditions it may function as ELR. (Japanese Utility Model Registration Application No. SHO 61-60945) However, such a retractor for seat belts which can fulfil functions of both ALR and ELR is arranged such that when the webbing has once been locked it may function as ALR, and therefore the seat belt wearer is restrained by the webbing so that he cannot change his posture freely and so he feels strong tightness. Further, the above-mentioned retractor has been disadvantageous in that, in order to pull out the webbing after it has once been locked, it is necessary to release or unlock the thus locked webbing thus necessitating the rewinding of it once in full length.